Most industrial processes, including almost all sources of friction, create some ultrasonic noise. For example, leaks in pipes, machinery defects, and electrical arcing produce ultrasonic sound waves. When the intensity of such ultrasonic noise exceeds an expected or "normal" level, this is an indication of a possible fault in the mechanical or electrical system. Thus, by continuously or periodically monitoring the intensity of ultrasonic noise produced by industrial machinery, maintenance personnel can detect faults and initiate appropriate repairs.
Current ultrasonic measurement instruments employ electroacoustical transducers to convert ultrasonic sound waves into ultrasonic electrical signals. Most of these instruments include circuitry that converts the ultrasonic electrical signals into audio-frequency electrical signals that are within the range of frequencies that can be detected by the human ear. The typical instruments employ headphones that convert the audio electrical signals into sound for an operator to hear.
The SonicScan ultrasonic measurement instrument, manufactured by Computational Systems, Inc., converts the ultrasonic electrical signals into digital electrical signals that can be displayed to the operator in a digital format and stored in computer memory. It is controlled by a microprocessor, and can be programmed to perform ultrasonic measurements that are specifically tailored to detect a specific type of fault on a particular type of machine or at a particular location on a machine. Further, the microprocessor can be programmed to configure the instrument for optimum performance with different types of transducers, such as contact and noncontact transducers.
As described in a pending application (U.S. Ser. No. 09/073,276, filed May 5, 1998), the SonicScan instrument system employs a route-based ultrasonic monitoring method. The system preferably uses a central computer that stores testing information concerning which machines to test, such as within a manufacturing plant, and that stores measurement parameters used to configure a portable ultrasonic sensing instrument. At the appropriate time, the testing information is loaded from the central computer into a portable, hand-held processing and storage unit, such as a personal data assistant (PDA). An operator is then prompted by the PDA to proceed to a test location. Once at the test location, the PDA provides the testing information and measurement parameters to the portable ultrasonic sensing instrument. The test is then performed by the operator with the portable ultrasonic sensing instrument, and the test results are downloaded from the portable sensing instrument to the PDA. Once all the tests along a particular route of testing locations have been performed, the test results are downloaded from the PDA to the central computer. In this manner, the results of the most recent set of tests can be compared to the results of previous tests to determine whether any machinery defects are present.